Field of the Invention
The present invention relates to density control of an image formed by an image forming apparatus.
Description of the Related Art
An electrophotographic image forming apparatus forms an image by converting image data based on a conversion condition, and forming an electrostatic latent image on a photosensitive member based on the converted image data, and then developing the electrostatic latent image using a developer in a developing device. Density of an image formed by the image forming apparatus varies according to a charge amount of the developer in the developing device. When the charge amount of the developer decreases, the density of the image formed by the image forming apparatus increases. In contrast, when the charge amount of the developer increases, the density of the image formed by the image forming apparatus decreases.
For the electrophotographic image forming apparatus, it is important to control the charge amount of the developer in the developing device to a target value so as to form an image of desired density. However, the charge amount of the developer in the developing device varies according to a temperature, a humidity, a time period for which the developer is agitated, and the like. In this connection, an image forming apparatus discussed in U.S. Pat. No. 6,418,281 updates a conversion condition based on a measurement result of a measurement image measured by a measurement unit, so as to form an image of desired density even if a change occurs in a charge amount of a developer. Density characteristics of the image formed by the image forming apparatus are corrected by updating the conversion condition.
For example, in a case where the conversion condition is updated each time the image forming apparatus forms images of a predetermined number of pages, the density characteristics of images can be corrected to desired density characteristics even while the image forming apparatus successively forms images.
However, if the conversion condition is updated after an image of an Nth page is formed and before an image of an (N+1)th page is formed while the image forming apparatus successively forms images, a difference between density of the image of the Nth page and density of the image of the (N+1)th page may increase. This occurs when the charge amount of the developer in the developing device greatly changes while the image forming apparatus successively forms images, and accordingly the density characteristics obtained after the conversion condition is updated greatly differs from the density characteristics obtained before the conversion condition is updated.